Self standing electrodes and methods for making thereof

ABSTRACT

The present disclosure relates to a method of making a composite product that may be used as a flexible electrode. An aerosolized mixture of nanotubes and an electrode active material is collected on a porous substrate, such as a filter, until it reaches a desired thickness. The resulting self-standing electrode may then be removed from the porous substrate and may operate as a battery electrode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. Pat. No.10,658,651, entitled “SELF STANDING ELECTRODES AND METHODS FOR MAKINGTHEREOF,” issued on May 19, 2020, the contents of which is herebyincorporated by reference in its entirety.

JOINT RESEARCH AGREEMENT

The presently claimed invention was made by or on behalf of the belowlisted parties to a joint research agreement. The joint researchagreement was in effect on or before the date the claimed invention wasmade, and the claimed invention was made as a result of activitiesundertaken within the scope of the joint research agreement. The partiesto the joint research agreement are 1) Honda Research Institute USA,Inc.; and 2) NanoSynthesis Plus, Ltd.

BACKGROUND

Single walled carbon nanotubes (SWNTs) as additives in various matriceshas become one of the most intensively studied areas for applications,owing to their excellent electrical and mechanical properties and highaspect ratio, which is crucial for composite materials. Among variousapplications, the exploitation of SWNTs as an additive material forperformance enhancement of battery electrodes is very promising. Thecore of mixing technologies is based on liquid process and includes fiverequired steps: a) synthesis of nanotubes, b) dispersion of nanotubes inthe proper solvent (de-aggregation), c) functionalization of thenanotube surfaces (protecting against aggregation), d) mixing withbinder and e) mixing with active material (preparing slurry). Theseprocesses not only are expensive, but also degrade nanotube properties,e.g. dispersion by ball milling, sonication etc., which leads toinevitable reduction of aspect ratio and the introduction of defects andas a result, requires more nanotube loading (wt %) for improvedperformance.

SUMMARY

In some embodiments, the present disclosure is directed to a method ofproducing a self-standing electrode. The method includes providing anaerosolized mixture of nanotubes and an electrode active materialpowder, and collecting the mixture on a porous substrate to form theself-standing electrode.

In some embodiments, the present disclosure is directed to a method ofproducing a self-standing electrode. The method comprises providing anaerosolized mixture of nanotubes and an electrode active materialpowder, providing at least a first porous substrate, directing theaerosolized mixture toward the first porous substrate, and collectingthe mixture on the first porous substrate to form the self-standingelectrode, wherein the self-standing electrode is free of binder andmetal-based current collector.

In some embodiments, the present disclosure is directed to a method ofproducing a self-standing electrode, the method comprising: aerosolizingan electrode active material to produce an aerosolized electrode activematerial powder; contacting the aerosolized electrode active materialpowder with single-walled carbon nanotubes in a carrier gas to form amixture of the single-walled carbon nanotubes and the aerosolizedelectrode active material powder; collecting the mixture on a surface;and removing the carrier gas, to form the self-standing electrodematerial that is a composite of single-walled carbon nanotubes and theelectrode active material, wherein the self-standing electrode is freeof binder and metal-based current collector.

In some embodiments, the present disclosure is directed to an apparatusfor producing a self-standing electrode, comprising: a single-walledcarbon nanotube synthesis reactor which produces single-walled carbonnanotubes; an aerosolizing reactor configured to aerosolize an electrodeactive material into an aerosolized electrode active material powder andconnected to the carbon nanotube synthesis reactor such that theaerosolized electrode active material powder is contacted with thesingle-walled carbon nanotubes in a carrier gas to form a mixture of thesingle-walled carbon nanotubes and the aerosolized electrode activematerial powder; and a collection chamber having a surface configured tocollect the mixture and remove the carrier gas so as to form theself-standing electrode material that is a composite of thesingle-walled carbon nanotubes and the electrode active material.

In some embodiments, the present disclosure is directed to aself-standing electrode, comprising a composite of an electrode activematerial and single-walled carbon nanotubes; wherein the self-standingelectrode does not contain binder material or a metal-based currentcollector material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram illustrating an exemplary method ofmaking a self-standing electrode according to an embodiment of thepresent disclosure.

FIG. 2 is a flow diagram illustrating an exemplary apparatus for makinga self-standing electrode according to an embodiment of the presentdisclosure.

FIG. 3 is a schematic view illustrating a vessel according to anembodiment of the present disclosure.

FIG. 4 is a flow diagram illustrating an exemplary apparatus for makinga self-standing electrode according to an embodiment of the presentdisclosure.

FIG. 5 is a schematic view of an apparatus according to an embodiment ofthe present disclosure.

FIG. 6 shows derivative thermogravimetric analysis (DTG) of carbonnanotubes synthesized according to an embodiment of the presentdisclosure.

FIG. 7 shows self-standing electrodes as collected from a poroussurface.

FIG. 8 shows self-standing electrodes after treating to increase thedensity.

FIG. 9 is a magnified side view of a treated self-standing electrode.

FIG. 10 is a magnified overhead view of the treated self-standingelectrode.

DETAILED DESCRIPTION

The present disclosure provides methods and apparatuses for theproduction of self-standing electrodes. Also provided are self-standingelectrodes comprising a mixture of nanotubes and electrode activematerials.

In an embodiment, a self-standing electrode is prepared by providing anaerosolized mixture of nanotubes and electrode active materials, anddirecting the aerosolized mixture to a porous substrate to form aself-standing electrode thereon comprising the mixed carbon nanotubesand the electrode active materials.

In some embodiments, the present disclosure is directed to a method ofproducing a self-standing electrode, the method comprising: aerosolizingan electrode active material to produce an aerosolized electrode activematerial powder; contacting the aerosolized electrode active materialpowder with single-walled carbon nanotubes in a carrier gas to form amixture of the single-walled carbon nanotubes and the aerosolizedelectrode active material powder; collecting the mixture on a surface;and removing the carrier gas, to form the self-standing electrodematerial that is a composite of single-walled carbon nanotubes and theelectrode active material.

As used herein, “electrode active material” refers to the conductivematerial in an electrode. The term “electrode” refers to an electricalconductor where ions and electrons are exchanged with an electrolyte andan outer circuit. “Positive electrode” and “cathode” are usedsynonymously in the present description and refer to the electrodehaving the higher electrode potential in an electrochemical cell (i.e.higher than the negative electrode). “Negative electrode” and “anode”are used synonymously in the present description and refer to theelectrode having the lower electrode potential in an electrochemicalcell (i.e. lower than the positive electrode). Cathodic reduction refersto a gain of electron(s) of a chemical species, and anodic oxidationrefers to the loss of electron(s) of a chemical species.

In a non-limiting example as shown in FIG. 1, self-standing electrodesfor Li-ion batteries are prepared by providing an aerosolized mixture ofcarbon nanotubes and electrode active materials at step S100, anddirecting the aerosolized mixture to a porous substrate at step S101 toform a composite self-standing electrode of a desired thickness thereonthat comprises the mixed carbon nanotubes and the electrode activematerials. Optionally, the self-standing electrode can be treated atstep S102 to, for example, increase the density of the self-standingelectrode. The self-standing electrode is self-supported, flexible, andcan optionally be cut to the desired dimensions of a battery electrode.The self-standing electrode is optionally free of binder and optionallycan be used without a metal-based current collector (typically aluminaor copper depending on the electrode type).

The apparatus for providing the aerosolized mixture of carbon nanotubesand electrode active materials is not limited in any way. In anillustrative example as shown in FIG. 2, an apparatus 5 for theproduction of self-standing electrodes is provided. The carbon nanotubesand the electrode active materials are added to a vessel 10. The carbonnanotubes and the electrode active materials may be individuallycollected from their respective manufacturing processes and directly orindirectly introduced from such processes into the vessel 10 at adesired ratio for the self-standing electrode. One or more carrier gases20 may then be introduced to the vessel 10 to aerosolize the mixture ofthe nanotubes and electrode active materials. The resulting mixedaerosolized stream 30 comprising the nanotubes and the electrode activematerials entrained in the carrier gas is directed to a porous substrate40, such as a filter. The carrier gas passes through the poroussubstrate 40 as gas stream 50 while the mixture of the nanotubes and theelectrode active material is captured on the surface of the poroussubstrate 40 to form the self-standing electrode 60. The self-standingelectrode 60 can be removed from the porous substrate 40 when it reachesthe desired thickness.

Optionally, the apparatus 5 may include a plurality of porous substrates40, 41 to allow for the continuous production of self-standingelectrodes 60, 61. Although only two porous substrates are shown, it isto be understood than any number of porous substrates may be included inthe apparatus 5. In a non-limiting example, when the flow of the mixedaerosolized stream 30 across the porous substrate 40 produces theself-standing electrode 60 of the desired thickness, a valve 33 may beadjusted to transfer the flow of the mixed aerosolized stream 30 to asecond porous substrate 41. The self-standing electrode 60 may beremoved from the first porous substrate 40 during formation of theself-standing electrode 61 on the porous substrate 41. When the flow ofthe mixed aerosolized stream 30 across the second porous substrate 41produces the self-standing electrode 61 of a desired thickness, thevalve 33 may be adjusted to transfer the flow of the mixed aerosolizedstream 30 back to the first porous substrate 40. The thickness and/orcross-sectional area of the self-standing electrode 61 may be the same,or different, than the cross-sectional area of the self-standingelectrode 60. For example, the self-standing electrode 61 may have agreater thickness and/or cross-sectional area than the self-standingelectrode 60.

It is to be understood that a variety of different methods may be usedfor automatically switching the valve 33 to redirect the flow of themixed aerosolized stream 30 from one porous substrate to the other.Illustrative examples of systems that may be used to adjust the valve 33to redirect the flow of the mixed aerosolized stream 30 include one ormore sensors for detecting the thickness of the self-standing electrodes60 and 61, one or more pressure sensors for monitoring a pressure dropacross the porous substrates 40 and 41 that corresponds to a desiredthickness of the self-standing electrodes 60 and 61, a timer thatswitches the valve 33 after a set time corresponding to a desiredthickness of the self-standing electrodes 60 and 61 for a given flowrate of the mixed aerosolized stream 30, and any combination thereof;after the one or more pressure sensors measures a pressure dropassociated with the desired thickness of the self-standing electrode 60or 61 on porous substrate 40 or 41, or after the one or more thicknesssensors detect the desired thickness of the self-standing electrode 60or 61 on porous substrate 40 or 41, or after the timer measures the settime corresponding to the desired thickness of self-standing electrode60 or 61 on porous substrate 40 or 41, the mixture is redirected fromone porous substrate to the other. It is also to be understood that theporous substrates 40 and/or 41 may have a cross-sectional area thatmatches the desired cross-sectional area required for use in the batterycell to be made with the self-standing electrode 60 and/or 61.Accordingly, the self-standing electrodes 60 and/or 61 would require nofurther processing of the cross-sectional area, such as cutting, beforeassembly in the final battery cell.

It is to be understood that the configuration of the vessel 10 is notintended to be limited in any way. In an illustrative example as shownin FIG. 3, the vessel 10 may be a pneumatic powder feeder, such as aventuri feeder that includes a hopper 11 for receiving the nanotubes andthe electrode active material therein. The vessel 10 may also include arotary valve 12 that feeds the nanotubes and the electrode activematerial into contact with the carrier gas 20 that is introduced to thevessel 10 to form the mixed aerosolized stream 30.

As shown in FIG. 4, the nanotubes and the electrode active material maybe individually aerosolized before mixing. For example, the nanotubesmay be provided in the vessel 10A and the electrode active material maybe provided in the vessel 10B. One or more carrier gases 20A may beintroduced to the vessel 10A to aerosolize the nanotubes, and one ormore carrier gases 20B may be introduced to the vessel 10B to aerosolizethe electrode active materials. An aerosolized stream 25A comprises thenanotubes entrained in the carrier gas 20A introduced to the vessel 10A,and an aerosolized stream 25B comprises the electrode active materialsentrained in the carrier gas 20B introduced to the vessel 10B. Theaerosolized stream 25A is mixed with the aerosolized stream 25B atjunction 27. The junction 27 may have any configuration capable ofcombining the aerosolized stream 25A and the aerosolized stream 25B intothe mixed aerosolized stream 30 that comprises a mixture of thenanotubes and the electrode active materials entrained in the carriergases. The mixed aerosolized stream 30 is directed to the poroussubstrate 40. The carrier gas passes through the porous substrate 40 asgas stream 50 while the mixture of the nanotubes and the electrodeactive material is captured on the surface of the porous substrate 40 toform the self-standing electrode 60. The self-standing electrode 60 canbe removed from the porous substrate 40 when it reaches the desiredthickness. The carrier gases 20A and 20B may be the same, or different,and may be introduced at the same or different flow rates. For example,the flow rates of the carrier gases 20A and 20B may be tailored to feedthe nanotubes and the electrode active material to the junction 27 atthe individual flow rates necessary to achieve the desired ratio ofnanotubes to electrode active material in the resulting self-standingelectrode 60. Although not shown, it is to be understood that more thanone porous substrate 40 may be provided as described with respect toFIG. 2.

As shown in FIG. 5, the nanotubes may be provided in an aerosolizedstream 25A directly from the vessel 10A that is configured as a nanotubesynthesis reactor for mixing with an aerosolized stream 25B of theelectrode active material from the source 106. Accordingly, theaerosolized stream 25A may be a product stream exiting the nanotubesynthesis reactor. For example, a carbon source or carbon precursor 130may be introduced to the vessel 10A in the presence of one or morecarrier gases 20A to form carbon nanotubes. The aerosolized stream 25Aof carbon nanotubes exits the reactor outlet 175 and travels down a pipeor tube 412 to a junction 27 where the aerosolized carbon nanotubes aremixed with the aerosolized stream 25B of the electrode active materials.Although the pipes forming the junction 27 intersect at a 90 degreeangle of intersection ‘a’, other angles of intersection a may be formed.In a non-limiting example, the angle of intersection a may be an acuteangle that facilitates flow of the resulting mixed aerosolized stream 30from the junction 27 to the porous substrate 40. Although not shown, itis to be understood that more than one porous substrate 40 (andcollection vessel 170) may be provided as described with respect to FIG.2.

As an alternative to the specific apparatus noted above where theelectrode active material is mixed with the nanotubes after thenanotubes are formed, the electrode active material can be mixed in situin a fluidized bed reactor or chamber with the nanotubes as thenanotubes are formed.

Carrier and fluidizing gases suitable for use with the presentdisclosure include, but are not limited to, argon, hydrogen, nitrogen,and combinations thereof. Carrier gases may be used at any suitablepressure and at any suitable flow rate to aerosolize the nanotubes andthe electrode active materials and transport the aerosolized mixture ofthe nanotubes and the electrode active materials to the porous substrateat a sufficient velocity to form the self-standing electrode on thesurface thereof. In some embodiments, the carrier gas may be argon,hydrogen, helium, or mixtures thereof. In some embodiments, the carriergas may comprise argon at a flow rate of 850 standard cubic centimetersper minute (sccm) and hydrogen at a flow rate of 300 sccm.

The type of nanotubes used in the present disclosure are not limited.The nanotubes may be entirely carbon, or they made be substituted, thatit is, have non-carbon lattice atoms. Carbon nanotubes may be externallyderivatized to include one or more functional moieties at a side and/oran end location. In some aspects, carbon and inorganic nanotubes includeadditional components such as metals or metalloids, incorporated intothe structure of the nanotube. In certain aspects, the additionalcomponents are a dopant, a surface coating, or are a combinationthereof.

Nanotubes may be metallic, semimetallic, or semi-conducting depending ontheir chirality. A carbon nanotube's chirality is indicated by thedouble index (n,m), where n and m are integers that describe the cut andwrapping of hexagonal graphite when formed into a tubular structure, asis well known in the art. A nanotube of an (m,n) configuration isinsulating. A nanotube of an (n,n), or “arm-chair”, configuration ismetallic, and hence highly valued for its electric and thermalconductivity. Carbon nanotubes may have diameters ranging from about 0.6nm for single-wall carbon nanotubes up to 500 nm or greater forsingle-wall or multi-wall nanotubes. The nanotubes may range in lengthfrom about 50 nm to about 10 cm or greater.

In a non-limiting example, the carbon nanotubes may be synthesized in areactor or furnace from a carbon source in the presence of a catalyst,at a temperature of about 1000 to about 1500° C., such as about 1300° C.

The present disclosure is not limited to the type or form of catalystsused for the production of carbon nanotubes. In various aspects, thecatalyst particles are present as an aerosol. In some aspects, thecatalyst materials are supplied as nanoparticles, comprising atransition metal, a lanthanide metal, or an actinide metal. For example,the catalyst may comprise a Group VI transition metal such as chromium(Cr), molybdenum (Mo), and tungsten (W), or a Group VIII transitionmetal such as iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru),rhodium (Rh), palladium (Pd), osmium (Os), Iridium (Ir), and platinum(Pt). In some aspects, a combination of two or more metals are used, forexample an iron, nickel, and cobalt mixture or more specifically a 50:50mixture (by weight) of nickel and cobalt. The catalyst may comprise apure metal, a metal oxide, a metal carbide, a nitrate salt of a metal,and/or other compounds containing one or more of the metals describedherein. The catalyst may be added to the reactor at about 0.1 atom % toabout 10 atom %, where atom % indicates the percentage of the number ofcatalyst atoms with respect to the total number of atoms in the reactor(catalyst and carbon precursor atoms).

Alternatively or in combination, a catalyst precursor may be introduced,wherein the catalyst precursor can be converted to an active catalystunder the reactor's conditions. The catalyst precursor may comprise oneor more transition metal salts such as a transition metal nitrate, atransition metal acetate, a transition metal citrate, a transition metalchloride, a transition metal fluoride, a transition metal bromide, atransition metal iodide, or hydrates thereof. For example, the catalystprecursor may be a metallocene, a metal acetylacetonate, a metalphthalocyanine, a metal porphyrin, a metal salt, a metalorganiccompound, or a combination thereof. For example, the catalyst precursormay be a ferrocene, nickelocene, cobaltocene, molybdenocene,ruthenocene, iron acetylacetonate, nickel acetylacetonate, cobaltacetylacetonate, molybdenum acetylacetonate, ruthenium acetylacetonate,iron phthalocyanine, nickel phthalocyanine, cobalt phthalocyanine, ironporphyrin, nickel porphyrin, cobalt porphyrin, an iron salt, a nickelsalt, cobalt salt, molybdenum salt, ruthenium salt, or a combinationthereof. The catalyst precursor may comprise a soluble salt such asFe(NO₃)₃, Ni(NO₃)₂ or Co(NO₃)₂ dissolved in a liquid such as water. Thecatalyst precursor may achieve an intermediate catalyst state in thecatalyst particle growth zone of the reactor, and subsequently becomeconverted to an active catalyst upon exposure to the nanostructuregrowth conditions in the nanostructure growth zone of the reactor. Forexample, the catalyst precursor may be a transition metal salt that isconverted into a transition metal oxide in the catalyst particle growthzone, then converted into active catalytic nanoparticles in thenanostructure growth zone.

The catalyst particles may comprise a transition metal, such as ad-block transition metal, an f-block transition metal, or a combinationthereof. For example, the catalyst particles may comprise a d-blocktransition metal such as an iron, nickel, cobalt, gold, silver, or acombination thereof. The catalyst particles may be supported on acatalyst support. In order to have catalyst particles on a catalystsupport, the catalyst support material may be introduced into thecatalyst material prior to adding the catalyst to the reactor.

The present disclosure is not limited to the type of carbon precursorsor carbon sources used to form carbon nanotubes such as one or morecarbon-containing gases, one or more hydrocarbon solvents, and mixturesthereof. Examples of carbon precursors include, but are not limited tohydrocarbon gases, such as methane, acetylene, and ethylene; alcohols,such as ethanol and methanol; benzene; toluene; CO; and CO₂. A fuel forcarbon nanotube synthesis and growth comprises a mixture of one or morecarbon precursors or carbon sources and one or more catalysts orcatalyst precursors.

The fuel or precursor may be injected at a range of about 0.05 to about1 ml/min, such as about 0.1 ml/min or about 0.3 ml/min, per injector. Insome embodiments, more than one injector may be used, for example atlarge scale. The gas flow rate may be about 0.1 to about 5 L/min ofhydrogen and/or about 0.2 to about 2 L/min helium or argon, such asabout 5 L/min hydrogen, or 0.3 L/min hydrogen and about 1 L/min argon.Without wishing to be bound to any particular theory, helium or argonmay be included in the carrier gas to dilute the hydrogen concentration,for example to keep the hydrogen concentration below the explosivelimit. Selection of a fuel injection rate and/or a gas flow rate maydepend, for example, on the reactor volume, as will be apparent to thoseof ordinary skill in the art. In some embodiments, more than one reactormay be used in conjunction. In some embodiments, the reactor temperatureprofile consists of a starting low temperature, an increase to a peak ora maximum, and then a decrease, preferably to the starting lowtemperature. Without wishing to be bound by any particular theory, for agiven reactor temperature profile, the injector position inside thereactor should be correlated with the precursor temperature so that theprecursor evaporates from the point of injection, without dropletformation or decomposition, as can be determined by those of ordinaryskill in the art, considering for example the boiling point anddecomposition. In some embodiments, the injector tip may be insertedinto the reactor, for example, by about 8 inches. The injectiontemperature, at the tip of the injector, may depend on the reactor orfurnace temperature and upon the depth of insertion of the injector intothe reactor or furnace. In some embodiments, the injection temperatureat the tip of the injector is about 750° C. In some embodiments, theinjector tip is inserted about 8 inches inside the reactor. The carbonnanotube reactor may be run for any suitable length of time to obtainthe product composition and thickness desired, as can be determined bythose of ordinary skill in the art, for example as long as there arestarting materials.

Carbon nanotubes synthesized according to the present disclosure may becharacterized using any suitable means known in the art, including butnot limited to derivative thermogravimetric analysis (DTG) and Ramanspectroscopy, such as for calculation of the G/D ratio, as is disclosedin U.S. Patent Application Publication No. 2009/0274609, which isincorporated herein by reference in its entirety. The Raman spectra ofSWNTs has three major peaks, which are the G-band at about 1590 cm⁻¹,D-band at about 1350 cm⁻¹, and the Radial breathing mode (RBM) at about100-300 cm⁻. RBM frequency is proportional to an inverse of the diameterof SWNTs and can thus be used to calculate the diameter of the SWNT.Normally, a red shift in RBM peak corresponds to an increase in the meandiameter of SWNTs. The tangential mode G-band related to theRaman-allowed phonon mode E_(2g) can be a superposition of two peaks.The double peak at about 1593 and 1568 cm⁻¹ has been assigned tosemiconductor SWNTs, while the broad Breit-Wigner-Fano line at about1550 cm⁻¹ has been assigned to metallic SWNTs. Thus, G-band offers amethod for distinguishing between metallic and semiconducting SWNTs. TheD-band structure is related to disordered carbon, the presence ofamorphous carbon, and other defects due to the sp²-carbon network. Theratio of the G-band to D-band in the Raman spectra (I_(G):I_(D) or G/Dratio) of SWNTs can be used as an index to determine the purity andquality of the SWNTs produced. Preferably, I_(G):I_(D) is about 1 toabout 500, preferably about 5 to about 400, more preferably greater thanabout 7. A representative, non-limiting example of DTG of carbonnanotubes synthesized according to the present disclosure is shown inFIG. 6.

Collecting the mixture of single-walled carbon nanotubes and aerosolizedelectrode active material powder on a surface and removing the carriergas may be carried out by any suitable means. The collecting surface ofthe porous substrate 40, 41 may be a porous surface, including but notlimited to a filter or a frit, where the pores are appropriately sizedto retain the mixture of carbon nanotubes and the electrode activematerial thereon to form the self-standing electrode while permittingpassage of the carrier and fluidizing gases. The carrier and fluidizinggases may be removed after passing through the surface and by way of anoutlet. In some embodiments, removal of the carrier gas may befacilitated by a vacuum source. With respect to filters, the filters maybe in the form of a sheet and may comprise a variety of differentmaterials including woven and non-woven fabrics. Illustrative filtermaterials include, but are not limited to, cotton, polyolefins, nylons,acrylics, polyesters, fiberglass, and polytetrafluoroethylene (PTFE). Tothe extent the porous substrate is sensitive to high temperatures, oneor more of the streams 25A, 25B, and 30 may be precooled with dilutiongases comprising a lower temperature and/or by directing one or more ofthe streams 25A, 25B and 30 through a heat exchanger prior to contactingthe porous substrate.

In some embodiments, the aerosolizing of the electrode active materialcomprises distributing an aerosolizing gas through a first porous fritand a bed of an electrode active material, in an aerosolizing chamber,to produce the aerosolized electrode active material powder. Theaerosolizing chamber may be constructed with an appropriately sizedporous material such that gas can pass through to enable aerosolizationbut that does not permit the active material to fall through the pores.The aerosolizing chamber is not limited to any particular configuration.Suitable aerosolizing gases include, but are not limited to, argon,helium, or nitrogen. In some embodiments, the aerosolizing gas may bethe same as the carrier gas.

In some embodiments, the electrode active material is selected fromgraphite, hard carbon, metal oxides, lithium metal oxides, and lithiumiron phosphate. In some embodiments, the electrode active material forthe anode may be graphite or hard carbon. In some embodiments, theelectrode active material for the cathode may be lithium metal oxides orlithium iron phosphate.

In a non-limiting example, the electrode active material may be anysolid, metal oxide powder that is capable of being aerosolized. In anillustrative example, the metal oxide is a material for use in thecathode of the battery. Non-limiting examples of metal oxides includeoxides of Ni, Mn, Co, Al, Mg, Ti and any mixture thereof. The metaloxide may be lithiated. In an illustrative example, the metal oxide islithium nickel manganese cobalt oxide (LiNiMnCoO₂). The metal oxidepowders can have a particle size defined within a range between about 1nanometer and about 100 microns. In a non-limiting example, the metaloxide particles have an average particle size of about 1 nanometer toabout 10 nanometers.

Metals in lithium metal oxides according to the present disclosure mayinclude but are not limited to one or more alkali metals, alkaline earthmetals, transition metals, aluminum, or post-transition metals, andhydrates thereof. In some embodiments, the electrode active material islithium nickel manganese cobalt oxide (LiNiMnCoO₂).

“Alkali metals” are metals in Group I of the periodic table of theelements, such as lithium, sodium, potassium, rubidium, cesium, orfrancium.

“Alkaline earth metals” are metals in Group II of the periodic table ofthe elements, such as beryllium, magnesium, calcium, strontium, barium,or radium.

“Transition metals” are metals in the d-block of the periodic table ofthe elements, including the lanthanide and actinide series. Transitionmetals include, but are not limited to, scandium, titanium, vanadium,chromium, manganese, iron, cobalt, nickel, copper, zinc, yttrium,zirconium, niobium, molybdenum, technetium, ruthenium, rhodium,palladium, silver, cadmium, lanthanum, cerium, praseodymium, neodymium,promethium, samarium, europium, gadolinium, terbium, dysprosium,holmium, erbium, thulium, ytterbium, lutetium, hafnium, tantalum,tungsten, rhenium, osmium, iridium, platinum, gold, mercury, actinium,thorium, protactinium, uranium, neptunium, plutonium, americium, curium,berkelium, californium, einsteinium, fermium, mendelevium, nobelium, andlawrencium.

“Post-transition metals” include, but are not limited to, gallium,indium, tin, thallium, lead, bismuth, or polonium.

In some embodiments, the method further comprises allowing the mixtureof single-walled carbon nanotubes and electrode active material in thecarrier gas to flow through one or more tubes connecting theaerosolizing reactor, the carbon nanotube synthesis reactor, and thecollection chamber. In some embodiments, the one or more tubes are atleast about 0.5″ O.D. stainless tubing.

The loading or weight % of carbon nanotubes in the compositeself-standing electrode product is based on the relative amounts of thenanotubes (or carbon source used to form the nanotubes) and theelectrode active material. It is within the level of ordinary skill inthe art to determine the relative starting amounts of carbon source,catalyst/catalyst precursor, and electrode active material that willafford a given loading or weight % of carbon nanotubes in the compositeself-standing electrode product. In a non-limiting example, theself-standing electrode may comprise from 0.1% to 4% by weight carbonnanotubes, and the balance the electrode active material and optionallyone or more additives. Optionally, the self-standing electrode maycomprise from 0.2% to 3% by weight carbon nanotubes, and the balance theelectrode active material and optionally one or more additives.Optionally, the self-standing electrode may comprise from 0.75% to 2% byweight carbon nanotubes, and the balance the electrode active materialand optionally one or more additives. Additives and/or dopants may bepresent for each range in an amount of 0 to 5% by weight. In anon-limiting example, the self-standing electrode consists essentiallyof the carbon nanotubes and the electrode active material powder. In anon-limiting example, the self-standing electrode consists of the carbonnanotubes and the electrode active material powder. For each of theranges, the self-standing electrode may be free of any binders. The lackof a binder results in a self-standing electrode with improvedflexibility. Further, it has been discovered that a higher carbonnanotube content increases the flexibility of the self-standingelectrode. Without being bound to any particular theory, this is likelydue to the webbed morphology of the self-standing electrode in whichthere is a webbed arrangement of carbon nanotubes with the electrodeactive material contained or embedded within the web.

In a non-limiting example, the self-standing electrode may comprise adensity of 0.9 to 1.75 g/cc. Optionally, the self-standing electrode maycomprise a density of 0.95 to 1.25 g/cc. Optionally, the self-standingelectrode may comprise a density of 0.75 to 2.0 g/cc. Optionally, theself-standing electrode may comprise a density of 0.95 to 1.60 g/cc.

In a non-limiting example, the self-standing electrode may comprise athickness of up to 750 μm following collection on the porous substrate.Optionally, the self-standing electrode may comprise a thickness of 50μm to 500 μm following collection on the porous substrate. Optionally,the self-standing electrode may comprise a thickness of from 100 μm to450 μm following collection on the porous substrate. Optionally, theself-standing electrode may comprise a thickness of from 175 μm to 250μm following collection on the porous substrate.

In some embodiments, the method of the present disclosure may furthercomprise treating the composite or self-standing electrode, includingbut not limited to pressing the composite or self-standing electrode.Without wishing to be bound to any particular theory, pressing mayincrease the density and/or lower the thickness of the self-standingelectrode, which may improve such properties as rate performance, energydensity, and battery life. Pressing of the self-standing electrodes maybe carried out by applying a force to achieve a desired thickness and/ordensity, such as by using a rolling press or calendaring machine, platenpress, or other suitable means, as will be known to those of ordinaryskill in the art. Any suitable force may be applied, to achieve adesired thickness, and/or density, and/or impedance, such as but notlimited to a force of about 1 ton, about 2 tons, about 3 tons, about 4tons, about 5 tons, about 6 tons, about 7 tons, about 8 tons, about 9tons, about 10 tons, about 15 tons, or any integer or range in between,such as between about 7 tons and about 10 tons. In some embodiments,pressing may be limited to pressing to a thickness of about 20 microns,about 30 microns, about 40 microns, about 50 microns, about 60 microns,about 70 microns, about 80 microns, about 90 microns, about 100 microns,about 150 microns, about 200 microns, about 250 microns, about 300microns, about 350 microns, about 400 microns, or any integer or rangein between. Without wishing to be bound by any particular theory, toothick of an electrode may be slow to produce energy or may not besuitably flexible. In some embodiments, it may be desirable to obtain anelectrode foil that is flexible without formation of oxide or cracks. Ifthe electrode is too thin, energy production may be rapid but it may bethe case that not enough energy is produced. In addition, it may bedesirable to regulate the distance between the rolls or rollers in arolling press or calendaring machine, or between the plates of a platenpress, by any suitable means known to those of ordinary skill in theart.

Determination of a suitable amount of pressing is within the level ofordinary skill in the art. As will be known to those of ordinary skillin the art, excessive pressing may cause the electrolyte to penetratethe electrode too much, as determined by measuring impedance and/orresistance to diffusion. As will be evident to those of ordinary skillin the art, it may be of interest to minimize the electrolyte diffusionresistance or coefficient for a given electrolyte, as measured byimpedance. In a non-limiting example, the thickness of the self-standingelectrode following pressing may be from 40% to 75% of the thickness ofthe untreated self-standing electrode, or the self-standing electrodefollowing collection on the porous substrate. Optionally, the thicknessof the self-standing electrode following pressing may be from 45% to 60%of the thickness of the untreated self-standing electrode, or theself-standing electrode following collection on the porous substrate.

In a non-limiting example, the density of the self-standing electrodefollowing pressing is increased by 40% to 125% of the density of theuntreated self-standing electrode, or the self-standing electrodefollowing collection on the porous substrate. Optionally, the density ofthe self-standing electrode following pressing is increased by 45% to90% of the density of the untreated self-standing electrode, or theself-standing electrode following collection on the porous substrate.

In some embodiments, the present disclosure is directed to an apparatusfor producing a self-standing electrode, comprising: a single-walledcarbon nanotube synthesis reactor which produces single-walled carbonnanotubes; an aerosolizing reactor configured to aerosolize an electrodeactive material into an aerosolized electrode active material powder andconnected to the carbon nanotube synthesis reactor such that theaerosolized electrode active material powder is contacted with thesingle-walled carbon nanotubes in a carrier gas to form a mixture of thesingle-walled carbon nanotubes and the aerosolized electrode activematerial powder; and a collection chamber having a surface configured tocollect the mixture and remove the carrier gas so as to form theself-standing electrode material that is a composite of thesingle-walled carbon nanotubes and the electrode active material. Allembodiments described for the method apply with equal force to theapparatus.

The surface may be configured to collect the mixture and remove thecarrier gas by any suitable means. The collecting surface may be aporous surface, including but not limited to a filter or a frit, wherethe pores are appropriately sized to permit passage of the carrier gasbut not the mixture of carbon nanotubes and electrode active material.The carrier gas may be removed after passing through the surface and byway of an outlet. In some embodiments, removal of the carrier gas may befacilitated by a vacuum source.

In some embodiments, the aerosolizing reactor comprises a verticalshaker, one or more gas inlets, one or more outlets, and a first porousfrit.

In some embodiments, the aerosolizing reactor is downstream of thecarbon nanotube synthesis reactor and upstream of the collectionchamber.

In some embodiments, the aerosolizing reactor is upstream of the carbonnanotube synthesis reactor and upstream of the collection chamber.

In some embodiments, the aerosolizing reactor is coincident with thecarbon nanotube synthesis reactor and upstream of the collectionchamber.

In some embodiments, the present disclosure is directed to aself-standing electrode, comprising a composite of an electrode activematerial and single-walled carbon nanotubes; wherein the self-standingelectrode does not contain binder material or a metal-based currentcollector material.

In some embodiments, the self-standing electrode comprises a webbedmorphology or a net. In some embodiments, a webbed morphology or a netis a webbed arrangement of carbon nanotubes with the electrode activematerial contained or embedded within the carbon nanotube web or net.

While the aspects described herein have been described in conjunctionwith the example aspects outlined above, various alternatives,modifications, variations, improvements, and/or substantial equivalents,whether known or that are or may be presently unforeseen, may becomeapparent to those having at least ordinary skill in the art.Accordingly, the example aspects, as set forth above, are intended to beillustrative, not limiting. Various changes may be made withoutdeparting from the spirit and scope of the disclosure. Therefore, thedisclosure is intended to embrace all known or later-developedalternatives, modifications, variations, improvements, and/orsubstantial equivalents.

Thus, the claims are not intended to be limited to the aspects shownherein, but are to be accorded the full scope consistent with thelanguage of the claims, wherein reference to an element in the singularis not intended to mean “one and only one” unless specifically sostated, but rather “one or more.” All structural and functionalequivalents to the elements of the various aspects described throughoutthis disclosure that are known or later come to be known to those ofordinary skill in the art are expressly incorporated herein by referenceand are intended to be encompassed by the claims. Moreover, nothingdisclosed herein is intended to be dedicated to the public regardless ofwhether such disclosure is explicitly recited in the claims. No claimelement is to be construed as a means plus function unless the elementis expressly recited using the phrase “means for.”

Further, the word “example” is used herein to mean “serving as anexample, instance, or illustration.” Any aspect described herein as“example” is not necessarily to be construed as preferred oradvantageous over other aspects. Unless specifically stated otherwise,the term “some” refers to one or more. Combinations such as “at leastone of A, B, or C,” “at least one of A, B, and C,” and “A, B, C, or anycombination thereof” include any combination of A, B, and/or C, and mayinclude multiples of A, multiples of B, or multiples of C. Specifically,combinations such as “at least one of A, B, or C,” “at least one of A,B, and C,” and “A, B, C, or any combination thereof” may be A only, Bonly, C only, A and B, A and C, B and C, or A and B and C, where anysuch combinations may contain one or more member or members of A, B, orC. Nothing disclosed herein is intended to be dedicated to the publicregardless of whether such disclosure is explicitly recited in theclaims.

Moreover, all references throughout this application, for example patentdocuments including issued or granted patents or equivalents; patentapplication publications; and non-patent literature documents or othersource material; are hereby incorporated by reference herein in theirentireties, as though individually incorporated by reference.

The following examples are put forth so as to provide those of ordinaryskill in the art with a complete disclosure and description of how tomake and use the present invention, and are not intended to limit thescope of what the inventors regard as their invention nor are theyintended to represent that the experiments below are all or the onlyexperiments performed. Efforts have been made to ensure accuracy withrespect to numbers used (e.g. amounts, dimensions, etc.) but someexperimental errors and deviations should be accounted for.

Examples

Production of flexible self-standing electrodes. The followingself-standing electrode examples set forth in FIGS. 7, 8, 9, 10, andTable 1 below were prepared in accordance with the present disclosureand are intended to illustrate the present disclosure without, however,limiting it.

A quartz tube having dimensions of 25 mm OD×22 mm I_(D)×760 mm lengthwas provided as the carbon nanotube reactor 10A for the apparatus 5(FIG. 5). The reactor 10A was aligned horizontally with a left endclosed with a barrier 402. However, the reactor 10A could be alignedvertically or at any angle therebetween. At the center of barrier 402, acarrier gas inlet 128 was provided for the carrier gas 20A and acatalyst/catalyst precursor inlet 132 was provided for thecatalyst/catalyst precursor 130. Both inlets 128 and 132 were positionedto the left of the section of the reactor 10A heated by the heat source119.

Reactor 10A was heated to a temperature of 1300° C. The carrier gas 20Aincluded a mixture of 850 sccm Ar and 300 sccm H₂ and was provided tothe reactor 10A via inlet 128. The catalyst precursor 130 compositionwas 80% ethanol, 20% methanol, 0.18% ferrocene, and 0.375% thiophene.The ethanol functioned both as a solvent for the ferrocene and as thecarbon source for growing the nanotubes. The catalyst precursor 130solution was injected at a rate of 0.3 ml/min via inlet 132 into thereactor carbon nanotube growth zone, where the ferrocene decomposed toiron catalyst particles and the ethanol was converted to a carbon sourcefor the growth of single-walled nanotubes on the iron catalysts. Thecarrier gas 20A transported the single-walled nanotubes through reactoroutlet 175 and into tube 412 as the first aerosolized stream 25A.

Lithium nickel manganese cobalt oxide (LiNiMnCoO₂) particles were usedas the electrode active material 106 and were loaded into aerosolizingchamber 10B on frit 407 to a height of about 5 mm, loading about 50 g.The carrier/aerosolizing gas 20B, argon, was provided at a rate of about2 L/min Ar through porous frit 407 via inlet 408 (1 L/min; bottom up)and inlets 409, 410 (1 L/min; tangential flows) in combination.Aerosolized suspended LiNiMnCoO₂ exits aerosolizing chamber 10B as thesecond aerosolized stream 25B via tube 413 and combines with the firstaerosolized stream 25A comprising the synthesized carbon nanotubestraveling through tube 412 at the junction 27, forming a mixture 30 ofaerosolized, suspended LiNiMnCoO₂ and carbon nanotubes in the carriergases. The mixture 30 travels through tube 416 into collection chamber170 via an inlet 418. The mixture 30 of LiNiMnCoO₂ and carbon nanotubesdeposits on the porous substrate 40, in this case a porous frit, as acomposite self-standing electrode 60, as the carrier gases 50 passthrough frit 40 and out an exhaust 420.

As shown in FIG. 7, two composite self-standing electrodes 60 werecollected from the porous substrate that included about 0.8 weight %single-walled carbon nanotubes and the balance LiNiMnCoO₂ particles. Theself-standing electrode 60 was then treated to increase the density bypressing (7 ton), to afford the treated self-standing electrode in FIG.8. As shown in the magnified view of FIG. 9, the treated self-standingelectrode 60 comprises a thickness of about 60 In addition, it is notedthat the self-standing electrode 60 shown in FIG. 9 (after pressing) isflexible and bent upwardly at the illustrated corner. This is likely dueto the web-like or non-woven fiber sheet formed by the carbon nanotubesas shown in FIG. 10 (after pressing). The carbon nanotube web surroundsthe LiNiMnCoO₂ particles to retain the LiNiMnCoO₂ particles thereinwithout the need for a binder in a flexible manner that allows forbending of the self-standing electrode.

As shown below in Table 1, several additional self-standing electrodeswere prepared using the same method with differing amounts ofsingle-walled nanotubes (the balance of the self-standing electrodebeing LiNiMnCoO₂ particles), as well as different thicknesses (ascollected from the porous substrate). The self-standing electrodes ofsamples 7-11 were treated following collection from the porous substrateby pressing to increase the density. Pressing of the self-standingelectrodes also resulted in a thickness reduction.

TABLE 1 Self-standing Original Original Electrode thickness densityComposition as of Self-Standing of Self-Standing Collected fromElectrode as Electrode as Thickness Density Porous Substrate: CollectedCollected of Self-Standing of Self-Standing Sample Weight Single-wallednanotube from Porous from Porous Electrode after Electrode after No.(mg) loading (weight %) Substrate (μm) Substrate (g/cc) Pressing (mm)Pressing (g/cc) 1 417 1.2 125 1.20 unknown unknown 2 612 1.1 200 1.11unknown unknown 3 572 1.1 200 1.03 unknown unknown 4 318 1.9 unknownunknown unknown unknown 5 138 1.5 unknown unknown unknown unknown 6 1511.6 unknown unknown unknown unknown 7 293 0.46 196 1.25 112 2.14 8 2650.73 211 1.05 148 1.49 9 339 0.41 244 1.16 128 2.20 10 811 0.21 434 1.56220 2.28 11 266 0.63 231 0.96 109 2.03

What is claimed is:
 1. A method of producing a self-standing electrode,the method comprising: aerosolizing an electrode active material toproduce an aerosolized electrode active material powder; contacting theaerosolized electrode active material powder with single-walled carbonnanotubes to form a mixture of the single-walled carbon nanotubes andthe aerosolized electrode active material powder; collecting the mixtureon a porous surface to form a composite of the single-walled carbonnanotubes and the electrode active material; and removing the compositefrom the porous surface to form a self-standing electrode, wherein theself-standing electrode is treated to increase the density thereof, andwherein the self-standing electrode comprises 0.1% to 4% by weightsingle-walled carbon nanotubes.
 2. The method of claim 1 wherein themixture comprises at least one carrier gas that passes through theporous surface as the mixture is collected on the porous surface.
 3. Themethod of claim 1 further comprising providing the single-walled carbonnanotubes from a carbon nanotube synthesis reactor.
 4. The method ofclaim 3, wherein the contacting of the aerosolized electrode activematerial powder with the single-walled carbon nanotubes occursdownstream of the carbon nanotube synthesis reactor and upstream of theporous surface.
 5. The method of claim 1, wherein the electrode activematerial is selected from graphite, hard carbon, lithium metal oxides,lithium iron phosphate, and combinations thereof.
 6. The method of claim1, wherein the self-standing electrode has a density after treatmentthat is 40% to 125% greater than a density of the self-standingelectrode prior to treatment.
 7. The method of claim 1, wherein theself-standing electrode comprises a webbed arrangement of thesingle-walled carbon nanotubes with the electrode active materialembedded within the single-walled carbon nanotube web.
 8. A method ofproducing a self-standing electrode, the method comprising: mixing afirst stream from a carbon nanotube synthesis reactor with a secondstream from an electrode active material powder source to provide athird stream, wherein the third stream comprises a mixture ofsingle-walled carbon nanotubes from the first stream and electrodeactive material powder from the second stream; collecting the mixture ona porous surface to form a composite of the single-walled carbonnanotubes and the electrode active material; and removing the compositefrom the porous surface to form a self-standing electrode, wherein atleast one of the first stream, the second stream, and the third streamis actively cooled with one or more dilution gases and/or by a heatexchanger prior to collecting the mixture on the porous surface.
 9. Themethod of claim 8, wherein the method comprises treating theself-standing electrode to increase the density thereof, and wherein theself-standing electrode comprises 0.1% to 4% by weight single-walledcarbon nanotubes.
 10. The method of claim 8 wherein the mixturecomprises at least one carrier gas that passes through the poroussurface as the mixture is collected on the porous surface.
 11. Themethod of claim 8, wherein mixing the electrode active material powderwith the single-walled carbon nanotubes occurs downstream of the carbonnanotube synthesis reactor and upstream of the porous surface.
 12. Themethod of claim 8, wherein the electrode active material is selectedfrom graphite, hard carbon, lithium metal oxides, lithium ironphosphate, and combinations thereof.
 13. The method of claim 9, whereinthe self-standing electrode has a density after treatment that is 40% to125% greater than a density of the self-standing electrode prior totreatment.
 14. The method of claim 8, wherein the self-standingelectrode comprises a webbed arrangement of the single-walled carbonnanotubes with the electrode active material embedded within thesingle-walled carbon nanotube web.
 15. A method of producing aself-standing electrode, the method comprising: providing an electrodeactive material powder in a vessel, wherein the electrode activematerial powder is provided in the vessel as a dry powder; contactingthe electrode active material powder with a first carrier gas to form afirst stream comprising the electrode active material powder and thefirst carrier gas; providing a product stream exiting directly from ananotube synthesis reactor, the product stream comprising carbonnanotubes and a second carrier gas; mixing the first stream and theproduct stream to provide a third stream, wherein the third streamcomprises a mixture of electrode active material powder from the firststream and carbon nanotubes from the product stream; collecting themixture on a porous surface to form a composite of the carbon nanotubesand the electrode active material powder, and removing the compositefrom the porous surface to form a self-standing electrode.
 16. Themethod of claim 15, wherein at least one of the first stream, theproduct stream, and the third stream is cooled prior to collecting themixture on the porous surface.
 17. The method of claim 16, wherein theself-standing electrode comprises 0.1% to 4% by weight single-walledcarbon nanotubes.
 18. The method of claim 15, wherein the methodcomprises treating the self-standing electrode to increase the densitythereof.
 19. The method of claim 18, wherein the self-standing electrodehas a density after treatment that is 40% to 125% greater than a densityof the self-standing electrode prior to treatment.
 20. The method ofclaim 15, wherein the self-standing electrode comprises a webbedarrangement of the carbon nanotubes with the electrode active materialembedded within the carbon nanotube web.